The present invention generally concerns the manufacture of electronic instruments having a plurality of printed circuit boards mounted therein. During the manufacture of electronic instruments, such as photoplethysmographic monitors, one or more printed circuit boards containing circuitry and various electronic components must be mounted on a chassis which is one part of the housing of the instrument. The standoff is a small often cylindrical part used to separate printed circuit boards from the chassis.
One of the problems associated with electronic instrument manufacture is the manufacture of an instrument which contains a plurality of printed circuit boards or other electronics boards, particularly those having one or more elements, such as input/output ports, which extend through the back plane of the chassis or housing. During the manufacture of such an instrument the printed circuit board cannot simply be lowered into the chassis from above in the same position in which it will be affixed to one or more standoffs. Rather, it is necessary to slide the printed circuit board in the plane of the printed circuit board so as to align the elements which extend through the back plane of the chassis or housing with their respective openings.
Therefore, there exists a need for a printed circuit board standoff which will facilitate the alignment and affixation of one or more printed circuit boards to a chassis. Prior art standoffs include those which are designed for the affixation of one printed circuit board through the use of internal threads which are mated to a screw which extends through the plane of the printed circuit board. Also known in the prior art are printed circuit board standoffs which use a keyhole to permit the mounting of a printed circuit board in a sliding manner. Additionally, prior art standoffs have included standoffs which use a friction fit such as the SNAP-TOP.RTM. from Penn Engineering and Manufacturing Corp. However, the prior art does not disclose a standoff which enables two printed circuit boards to be stacked separated from the chassis and from one another where at least one of the printed circuit boards is to be mounted using a keyhole slot and keyhole.